There are numerous applications for imaging sensors that provide infrared search and track (IRST), targeting or standoff reconnaissance functions, such as on an aircraft including an unmanned aerial vehicle (UAV) platform for standoff reconnaissance or on a jet aircraft for IRST, targeting (i.e., target location and designation) and standoff reconnaissance (e.g., survey or observation to collect image information). Additionally, some IRST systems include laser range-finding, and/or coherent laser detection and ranging (LADAR) capabilities. As its name indicates, an IRST system operates generally in the infrared wavelength range; however visible wavelength sensing capability is typically also desired within the IRST sensor.
Each of the IRST function, standoff reconnaissance function and targeting function has unique system requirements, including the significantly different fields of regard. For example, the IRST field of regard is very wide in azimuth (horizontal), but generally forward looking, whereas the standoff reconnaissance field of regard is wide in pitch (horizontal), but generally side looking. The targeting field of regard is generally very wide in elevation, and can extend from many degrees above the local horizon (forward) to many degrees past (behind) the local nadir (vertical) by as much as 60 degrees.